[wicker]

It's been a really fun break!

I'm getting interested in super low frequency signals so I looked up the E202 Very Low Frequency (<10kHz) receiver[1] and laid out/built a variation of it.[2] Right now the whole thing is a broadband receiver with no antenna (obviously) and the whole circuit board assembly is functionally acting like a microphone. I can hear when I touch any component or move my hand around in the air. I'm going to add a 60Hz notch file and then take it out to the middle of nowhere.

I think it would be awesome to go find a pipeline to use as an antenna...

Next project is to take my BlueROV[3] and build a hydrophone array[4] for it so a friend and I can see if a underwater acoustics engineer friend and I can use it to track other objects (like a remote-controlled toy boat) in the water. I've been doing some Kivy visualization of an accelerometer and gyro (MPU9255) and I think we could use matplotlib's interactive mode or something in Kivy (maybe) to visualize it all in realtime.

There's nothing cutting edge here but I've done a bunch of radio frequency (RF) stuff like GPS and WiFi and I'm really enjoying how tangible audio seems in comparison. Just having fun with low frequencies, basically.

[1] http://www.vlf.it/romero2/explorer-e202.html

[2] https://github.com/wicker/e202var-natural-radio-receiver

[3] https://www.bluerobotics.com/store/rov/bluerov-r1/

[4] http://www.dosits.org/files/dosits/hydrophone_instruc_w_imag...

[benjamincburns]

FWIW, you may wish to add a 50Hz notch filter as well. If you're in North America 50Hz noise won't be as much of an issue, but if your receiver is sensitive enough there's likely still enough of it floating around from various DC-AC inverters and the like. Of course, if you've got a good enough tuner you can likely just measure the noise in that "band" yourself.

Re: using a pipeline as an antenna - I wonder how difficult (or illegal) it would be to use mains power lines. My RF-foo is only marginally above white-belt, but I'd imagine that a fair amount of low frequency signal would make it through the transformers.

[wicker]

Thanks for the suggestion, I'll do that! I posted partly in hopes that somebody would reply and solve problems I didn't know I had. That's the joy of being totally new to this stuff. I don't know what I don't know. :D

Re: using mains power lines... I actually have a friend who might be able to answer that, so I'll ask him. We were also considering transmission towers, since plenty of the hikes I know will take me across a clearcut for the transmission lines, and I can get some altitude with good, unobstructed views.